Jet assembly for diffusion pump



Dec. 24, 1963 R. F. SALAT 3,115,298

JET ASSEMBLY. FOR DIFFUSION PUMP Filed Dec. 12, 1961 ROBERT F'- sALAf A T TOENE).

United States Patent 3,115,298 JET ASSEMBLY FOR DIFFUSION PUMP Robert F. Salat, East Northport, N.Y., assignor to Vactronic Lab. Equipment, Inc., East Northport,

' Filed Dec. 12, 1961, Ser. No. 158,704

Claims. 01. 230-101 The present invention relates to an improved diffusion pump of the type having a plurality of concentrically arranged fractionating columns disposed within a vertical pump barrel, and more specifically, to improved spacing means for maintaining said columns in spaced relation to each other and to the pump barrel. It is adapted to be used with vapor diffusion pumps of relatively small size and weight, wherein disassembling the pump for cleaning purposes is contemplated as part of normal maintenance procedure, hence where simple rapid means for aligning and reassembling the parts is highly important.

The usual vapor diffusion pump employs concentric columns or chimneys extending upwardly within a pump barrel, with the bottom of the pump casing defining a boiler for a volatile liquid. The vaporized liquid passes upwards through these columns, then is deflected downwardly and outwardly by a configuration of baflles or skirts, the vapor being directed to the inner walls of the pump barrel, there liquifying and flowing downwardly to the boiler section for repetition of the cycle. It is well understood in the art that the efiiciency of a pump of this type depends to a great extend on the elimination of turbulence within the system, which then permits greater speed in the boiler cycle, with a minimum of backstreaming. Such a device commonly requires rather frequent maintenance, with disassembly, cleaning and reassembly. Thus, means must be provided for accurate alignment of the concentric columns each time the device is reassembled, otherwise turbulence will be introduced into the system. It will be appreciated that the alignment means must have minimum structural dimensions, so that there is provided an unobstructed flow path for vapor within the system, which will avoid local eddies. Furthermore, such simple alignment means permits of maintenance and assembly by relatively unskilled personnel and with less down-time.

It is therefore a primary object of the present invention to provide an improved vapor diffusion pump having novel alignment means for the concentric fractionating columns.

It is a further object of the present invention to provide means for rapid disassembly, cleaning and reassembling of a vapor diffusion pump.

It is yet a further object of the present invention to provide a diffusion pump with relative minimal turbulence in the jet stream.

These and other objects will be pointed out with further particularity in the following description taken in conjunction with the accompanying drawing.

In the drawing:

FIG. 1 is a longitudinal cross-section of the device in the assembled position.

FIG. 2 is a cross-section taken along line 22 of FIG. 1.

FIG. 3 is a partially exploded view in perspective of a device of the present invention.

FIG. 4 is a fragmentary sectional plan view illustrating an alternative form of releasable fastening means for the spacing rods of the present invention.

Referring now more specifically to the drawing, there is shown in FIG. 1, a diffusion pump designed for producing a high vacuum, wherein cylindrical pump barrel 112 has concentrically disposed therein fractionating columns 14, 16 and 18. Column 14 has formed thereon an annular downwardly deflecting baffle 20 whose lower rim 22 is proximate to the upper edge 24 of column 16, to provide an annular jet opening 26 which is flared downwardly and outwardly. Similarly, column 16 is provided with baffle 28 which overlies upper rim 30 of column 18 to define jet opening 32. Cap 34 is disposed concentrically above column 14, being mounted on threaded shaft 36 disposed on spider 38, spider 38 being provided with large openings 39, to permit passage of vapor therethrough. Lower rim 40 of cap 34 overlaps upper edge 42 of column 14 to define jet opening 42a. Cap nut 35 secures the cap 34 to shaft 36. Fractionating oil 43 is volatilized by heater element 44, the vapors being deflected downward by jet openings 26, 32 and 42a, thereby entraining gas molecules brought into the pump through inlet 46, which communicates to the system to be evacu- \ated. Exhaust port 48 connects to a conventional forepump unit (not shown).

As shown in FIG. 3, taken in conjunction with FIG. 1, columns 14, 16 and 18, each have formed therein a pair of transverse diametric-al openings 5011-5011, 52a52b, and '54a54b, respectively. These openings are transversely aligned when the columns are in the assembled position. Spacing rod '56 is passed through these pairs of openings, as shown in FIG. 1. Rod 56 is machined to a length closely approximating that of the inner diameter of barrel 12. A pair of snap rings 58 engage annular grooves in rod 56 to secure the rod. A second spacing rod 60 is disposed transversely within the pump barrel in a manner similar to rod 56 but at a radial angle thereto and at some axial distance thereto. Rod 60 is passed through a second set of paired openings in columns 14, 16 and 18, 62a62b, 64a64b, 66a66b, as shown in FIG. '2, and secured by snap rings 63'. It will be apparent that rods 56 and 60 co-operate to space columns 14, 16 and 18 in proper alignment within the pump casing, and prevent any lateral displacement. Therefore, the concentricity of the columns is maintained at all times. Spacing rods 56 and 60' also maintain the columns in proper axial alignment, since there can be no translational movement of one column relative to the other, as the original position of the columns is set by the juxtaposition of base 68 of column 18 upon plate 70 of pump barrel 12. In lieu of snap rings 58, 63, other securing means may be employed; for example, the rods 56 and 60' may be provided with threaded ends 57 and 65, respectively, to receive conventional nut members 59* and 67, respectively (FIG. 4).

It should be further noted that the simple juxtaposition of spacing rods '56 and 60 also aligns the different jet openings 22, 32, and 42 correctly, without providing any obstruction in these openings, in contradistinotion to devices currently employed, wherein support members or spacing members are placed in these jet openings. This arrangement in the present invention adds greatly to the efficiency of the device as it eliminates turbulence at a point where it would be likely to occur, namely, at the juncture of the vapor coming from the jet opening, and the entrained gas molecules coming from the high vacuum area. Furthermore, this uniformity of alignment preserves the concentricity of the columns and assures uniform distribution of vapor pressure through each of the respective jet openings. It will be appreciated that the great simplicity of the parts used makes for rapid disassembly, cleaning and reassembly of the device.

There has been disclosed heretofore the best embodiment of the invention presently contemplated and it is to be understood that various changes and modifications may be made by those skilled in the art without departing from the spirit of the invention.

What is claimed is:

1. A diffusion pump comprising:

a vertical pump barrel having an exhaust port in communication with the interior thereof;

a plurality of concentrically arranged fractionation columns disposed within said vertical pump barrel, each of said columns being provided with a first and a second pair of transverse diametrical openings; and

spacing means for maintaining said columns in spaced relation to each other and to said barrel, said space ing means comprising first and second spacing rods adapted to be disposed horizontally within said barrel, said rods being substantially equal in length to the inside diameter of said barrel, said first rod being positioned in the first pairs of transverse tdiametrical openings formed in said columns, said first pair of openings being transversely aligned when said columns are in the assembled condition, said second rod being positioned in the second pairs of transverse diametrical openings'formed in said columns, said second pairs of openings being displaced axially from said first pairs of openings, said second pairs of openings being transversely aligned when said columns are in the assembled condition.

2. The device as in claim 1 including releasable fastening means disposed on the terminal portions of each of said spacing rods.

3. A device as in claim 2 wherein said releasable fastening means comprise threaded portions formed on said terminal portions of said rods, and nuts disposed on said threaded portions.

4. A device as in claim 2 wherein said releasable fastening means comprise an annular groove formed on said respective terminal portions of said rods, and retaining rings disposed in said annular grooves.

5. A device as in claim 2 wherein said radial angle between said first and said second pairs of openings is 90 degrees and said first and second spacing rods are positioned below said exhaust port.

References Cited in the file of this patent UNITED STATES PATENTS 1,791,105 Seitz Feb. 3, 1931 2,489,058 Stoltenberg Nov. 22, 1949 2,793,008 Donegan May 21, 1957 2,903,181 Giepen Sept. 8, 1959 

1. A DIFFUSION PUMP COMPRISING: A VERTICAL PUMP BARREL HAVING AN EXHAUST PORT IN COMMUNICATION WITH THE INTERIOR THEREOF; A PLURALITY OF CONCENTRICALLY ARRANGED FRACTIONATION COLUMNS DISPOSED WITHIN SAID VERTICAL PUMP BARREL, EACH OF SAID COLUMNS BEING PROVIDED WITH A FIRST AND A SECOND PAIR OF TRANSVERSE DIAMETRICAL OPENINGS; AND SPACING MEANS FOR MAINTAINING SAID COLUMNS IN SPACED RELATION TO EACH OTHER AND TO SAID BARREL, SAID SPACING MEANS COMPRISING FIRST AND SECOND SPACING RODS ADAPTED TO BE DISPOSED HORIZONTALLY WITHIN SAID BARREL, SAID RODS BEING SUBSTANTIALLY EQUAL IN LENGTH TO THE INSIDE DIAMETER OF SAID BARREL, SAID FIRST ROD BEING POSITIONED IN THE FIRST PAIRS OF TRANSVERSE DIAMETRICAL OPENINGS FORMED IN SAID COLUMNS, SAID FIRST PAIR OF OPENINGS BEING TRANSVERSELY ALIGNED WHEN SAID COLUMNS ARE IN THE ASSEMBLED CONDITION, SAID SECOND ROD BEING POSITIONED IN THE SECOND PAIRS OF TRANSVERSE DIAMETRICAL OPENINGS FORMED IN SAID COLUMNS, SAID SECOND PAIRS OF OPENINGS BEING DISPLACED AXIALLY FROM SAID FIRST PAIRS OF OPENINGS, SAID SECOND PAIRS OF OPENINGS BEING TRANSVERSELY ALIGNED WHEN SAID COLUMNS ARE IN THE ASSEMBLED CONDITION. 